The present invention relates to television cameras and more particularly to solid-state television cameras which use solid-state image pick-up elements.
The solid-state image pick-up element is compact in size and light in weight in comparison with image pick-up tubes which have been conventionally used in television cameras. Thus, its use is very effective for manufacturing a television camera which is compact in size and light in weight. Therefore, it is expected that these solid-state image pick-up elements will be used especially for shoulder cameras which are carried on the shoulders of cameramen.
In general, it is preferable for a shoulder camera to have an outer shape such that the camera may be set on the shoulder of a cameraman in a stable manner to facilitate easy and smooth operation. Such an outer appearance requires that it be short in the direction perpendicular to the optical axis of the camera, and long in the direction along the optical axis. The ratio of these lengths must be able to be arbitrarily selected.
However, a conventional solid-state television camera is so constructed that a printed circuit board having a solid-state image pick-up element such as a CCD (charge coupled device) and its peripheral circuits is arranged in a direction perpendicular to the optical axis of the camera, and the incident light is introduced to the solid-state image pick-up element directly. Consequently, the outer shape of the camera is such that it is long in the direction perpendicular to the optical axis of the camera. Thus, this type of camera is difficult to use as a shoulder camera and is usually supported on a tripod.
An example of a conventional solid-state television camera with such a shape is schematically shown in FIG. 1. In FIG. 1, the camera is shown from above with its upper cap removed. In the television camera shown in FIG. 1, an image taking lens 1 is disposed in front of the camera, and behind the camera is disposed a printed circuit board 2 on which are in turn mounted a CCD 3 and its peripheral circuits in a direction perpendicular to the optical axis of the lens 3. Behind the camera further are disposed printed circuit boards 4, 5, 6, 7 and 8 on which are mounted digital circuits, image signal processing circuits and so on. In addition to the CCD 3, many components such as a driving circuit, an input and output circuit and so on are arranged on the printed circuit board 2 in the immediate vicinity of the CCD 3 to provide various electrical characteristics. Thus, the printed circuit board 2 must be arranged in a direction perpendicular to the optical axis as shown in FIG. 1, resulting in an outer shape unsuitable for a shoulder camera as has been described above.
Besides its outer shape, the conventional solid-state television camera as shown in FIG. 1 has problems as described below. The terminals of the printed circuit board 2 with the CCD 3 mounted on it are connected to the terminals of the printed circuit boards 4 and 8 on which are mounted digital circuits, image signal processing circuits and so on. Thus, a considerable space is required for wiring between each printed circuit board, and especially between the printed circuit board 2 and the printed circuit boards 4 and 8, adversely affecting the compactness of the television camera. Further, since the number of printed circuit boards is large, the number of input and output connectors for the printed circuit boards is also large. The reliability is degraded due to the large number of connection points between each printed circuit board and synchronous noise is increased due to long wiring. The generation of such synchronous noise may be explained in the manner described below. Clock pulses must be supplied to a transfer electrode for actuating the solid-state image pick-up element 3, ans this supply of the clock pulses may be performed by a clock pulse generating circuit (clock driver) generally disposed inside the camera. An equivalent circuit for the transfer electrode in this case is a capacitor. When a pulse current is supplied to this capacitor, a large discharge current resulting from the change in the pulse voltage flows through the wiring. This discharge current electrostatically or electromagnetically generates outer radiation, adversely affecting the wiring. When the wiring is long, the impedance is made greater. This results in the generation of noise (synchronous noise) due to the above-mentioned outer radiation and this noise appears on the screen.
For better performance or higher resolution in a solid-state television camera, it is also known to use a bias light. However, in a conventional solid-state television camera as shown in FIG. 1, the CCD 3 is arranged in a drection perpendicular to the optical axis. Thus the bias light must be arranged between the image taking lens 1 and the CCD 3. This requires additional space, resulting in a bigger camera.
The television camera shown in FIG. 1 is a monochrome solid-state television camera using a single solid-state television image pick-up element. However, in the case of a two-plate type solid-state television camera using two solid-state image pick-up elements, an optical system is required for dividing the light from the image taking lens 1, and two CCDs are required for receiving the divided light rays. In such a case, one of the CCDs is arranged at a constant angle with respect to the optical axis. This arrangement of two CCDs requires more space. In general, a shoulder camera does not adopt a system in which the image taking lens is oriented toward the subject while viewing through the viewfinder, but a system in which the camera is manipulated while viewing the subject with the naked eye. Thus, it is sometimes impossible to photograph an intended subject which is very close. In order to prevent this problem, it is preferable that the shoulder camera be operable while viewing through the viewfinder. However, since the CCD 3 is arranged in a direction perpendicular to the optical axis in the conventional camera shown in FIG. 1, it is difficult to adopt a system which uses a viewfinder.